CN103364784A - Looking-around synthetic aperture imaging radar - Google Patents

Abstract

The invention provides a looking-around synthetic aperture imaging radar. The imaging radar comprises a launch unit 1, a receiving, amplifying, down-conversion and filtering unit 2, a signal processing and imaging unit 3, a display unit 4, a radio frequency signal generating unit 5, a control unit 6 and a power device 7 controlling rotating of a receiving antenna and a transmitting antenna. The looking-around synthetic aperture imaging radar is installed on a top platform of a ship, the transmitting antenna transmits electromagnetic waves to the periphery of the ship in the 360-degree direction, the receiving antenna receives electromagnetic wave signals reflected back by targets and sea waves and performs amplifying, down-conversion and sampling on the signals, and after arc synthetic aperture imaging signal processing, imaging processing and the like are preformed, an image display circuit displays the targets and the sea state information around the ship. The looking-around synthetic aperture imaging radar can replace an S/X wave band ship navigation radar widely applied currently and is used for guiding the ship to sail, ship collision is avoided, meanwhile, the looking-around synthetic aperture imaging radar has the function of inverting ocean kinetic parameters (waves and currents) around the ship, and therefore safety of navigation of the ship is ensured.

Description

A kind of synthetic aperture imaging radar of looking around

Technical field

The invention belongs to the marine navigation technical field, particularly a kind of for the synthetic aperture imaging radar of looking around with the assurance marine operation safety of target and sea situation around the monitoring boats and ships.

Background technology

Tradition boats and ships guiders (such as boat-carrying X/S wave band navar) adopt pulse radar to realize the boats and ships monitoring of target on every side, the guider of this mode has following shortcoming: 1. because the restriction of time-bandwidth product, the words that range resolution is high, operating distance diminishes, operating distance is large, the range resolution variation; 2. belong to real aperture radar, its azimuthal resolution is subjected to the restriction of antenna aperture, is difficult to be further enhanced; 3. more employing magnetron technology belongs to incoherent radar, and the emissive power of often having relatively high expectations causes electromagnetic interference (EMI) easily; 4. be subject to easily other with the interference of frequency range work radar; 5. the closely blind area that has large (hundreds of rice); 6. can not the direct detection target velocity; 7. obtain the ability of boats and ships periphery drive marine mathematic(al) parameter when not possessing navigation work.

Summary of the invention

The present invention is directed to the problems referred to above, a kind of synthetic aperture imaging radar of looking around is proposed, the present invention is installed on the top platform of boats and ships, its emitting antenna while rotating to boats and ships 360 degree orientation transponder pulse ripples or linear frequency modulation continuously/pulsating wave, receiving antenna receive successively while rotating the pulsating wave that reflected by target or linear frequency modulation continuously/pulsating wave, the propulsion system control that the rotation of dual-mode antenna is rotated by the control dual-mode antenna, this signal is amplified, down coversion, sampling, after signal processing and imaging etc. are processed, demonstrate boats and ships target information on every side by image-display units, avoid ship collision, guiding ship's navigation, thereby the safety of assurance boats and ships.

The technical solution used in the present invention is as follows:

A kind of synthetic aperture imaging radar of looking around is characterized in that: comprise transmitter unit 1, reception, amplification, down coversion and filter unit 2, signal is processed and image-generating unit 3, display unit 4, radio frequency signal generation unit 5, control module 6, the propulsion system 7 that the control dual-mode antenna rotates;

Control module 6 respectively with transmitter unit 1, reception, amplification, down coversion and filter unit 2, display unit 4, radio frequency signal generation unit 5, the propulsion system 7 that the control dual-mode antenna rotates connect;

Transmitter unit 1 respectively with radio frequency signal generation unit 5, the propulsion system 7 that the control dual-mode antenna rotates connect; Reception, amplification, down coversion and filter unit 2 respectively with radio frequency signal generation unit 5, signal is processed and image-generating unit 3, propulsion system 7 connections that the control dual-mode antenna rotates; Signal is processed to be connected with image-generating unit and is connected with display unit 4.

Described transmitter unit 1 comprises frequency-modulated wave generator, up-converter circuit, power amplification circuit and the emitting antenna that connects successively; The output terminal of radio frequency signal generation unit 5 is connected with the input end of up-converter circuit.

Described reception, amplification, down coversion and filter unit 2 comprise receiving antenna, amplifying circuit, down coversion and the filtering circuit that connects successively; The output terminal of radio frequency signal generation unit 5 is connected with the input end of down coversion and filtering circuit.

Described signal is processed to be connected with image-generating unit and is comprised digital sample circuit, imaging signal processing and the imaging circuit that connects successively.

The propulsion system 7 that described control dual-mode antenna rotates comprise antenna rotating platform and control circuit thereof; Be fixed with rotating shaft on the antenna rotating platform, control circuit control emitting antenna and receiving antenna rotate around the axle center of rotating shaft.

Above-mentioned radio frequency signal generation unit 5 is provided with the control circuit that the control radiofrequency signal produces.

Above-mentioned transmitter unit 1 be provided with gating pulse ripple or linear frequency modulation continuously/control circuit that pulsating wave produces.

Above-mentioned digital sample circuit is provided with the control circuit of control figure sampling.

Above-mentioned control circuit comprises crystal oscillator, micro-chip processor, FPGA treatment circuit.

Compared with prior art, the present invention can solve the contradiction between existing navigator operating distance and range resolution, and by circular arc synthetic aperture detection mode, makes it substantially not have closely blind area, possess higher azimuth direction resolution, improve remote detection performance; In navigation work, have the detectivity of drive marine mathematic(al) parameter (wave, ocean current) concurrently; Based on the coherent radar system, utilize to encircle and sweep the Doppler shift modulation of introducing simultaneously, make it possess the preferably ability of anti-co-channel interference, provide quick precision target information to boats and ships, comprise the velocity information of target, the guiding ship's navigation, avoid ship collision, ensure safety of ship.

Description of drawings

Fig. 1 is circuit block diagram of the present invention.

Fig. 2 is the circuit theory diagrams of transmitter unit among the present invention.

Fig. 3 is reception among the present invention, amplification, down coversion and filter unit, and signal is processed and image-generating unit, the connection of display unit and schematic diagram.

Fig. 4 is the synoptic diagram of radar beam rotation sweep sea-surface target among the present invention.

Fig. 5 is the use view that the present invention is installed in the boats and ships top platform.

Fig. 6 is static target Doppler history synoptic diagram in the present invention on the sea.

Fig. 7 is wave stream inverting data pretreatment process figure of the present invention.

Fig. 8 is wave stream inverting process flow diagram of the present invention.

Wherein, 1-transmitter unit, 2-reception, amplification, down coversion and filter unit, 3-signal is processed and image-generating unit, 4-display unit, 5-radio frequency signal generation unit, 6-control module, the propulsion system that 7-control dual-mode antenna rotates.

Embodiment

One, below in conjunction with accompanying drawing, the invention will be further described.

Referring to Fig. 1, the present invention includes transmitter unit 1, reception, amplification, down coversion and filter unit 2, signal is processed and image-generating unit 3, display unit 4, radio frequency signal generation unit 5, control module 6, the propulsion system 7 that the control dual-mode antenna rotates;

Control module 6 respectively with transmitter unit 1, reception, amplification, down coversion and filter unit 2, display unit 4, radio frequency signal generation unit 5, the propulsion system 7 that the control dual-mode antenna rotates connect;

Transmitter unit 1 respectively with radio frequency signal generation unit 5, the propulsion system 7 that the control dual-mode antenna rotates connect; Reception, amplification, down coversion and filter unit 2 respectively with radio frequency signal generation unit 5, signal is processed and image-generating unit 3, propulsion system 7 connections that the control dual-mode antenna rotates; Signal is processed to be connected with image-generating unit and is connected with display unit 4.

Transmitter unit 1 comprises frequency-modulated wave generator, up-converter circuit, power amplification circuit and the emitting antenna that connects successively; The output terminal of radio frequency signal generation unit 5 is connected with the input end of up-converter circuit.

Reception, amplification, down coversion and filter unit 2 comprise receiving antenna, amplifying circuit, down coversion and the filtering circuit that connects successively; The output terminal of radio frequency signal generation unit 5 is connected with the input end of down coversion and filtering circuit.

Signal is processed to be connected with image-generating unit and is comprised digital sample circuit, imaging signal processing and the imaging circuit that connects successively.

The propulsion system 7 that the control dual-mode antenna rotates comprise antenna rotating platform and control circuit thereof; Be fixed with rotating shaft on the antenna rotating platform, control circuit control emitting antenna and receiving antenna rotate around the axle center of rotating shaft.

Among Fig. 2, under the instruction effect of the control signal that control module 6 sends, the frequency-modulated wave generator produce the pulsating wave of certain bandwidth or linear frequency modulation continuously/the pulsed base band signal, radiofrequency signal generator in the radio frequency signal generation unit 5 produces the radio-frequency signal source of certain frequency, the chirp baseband signal is modulated on the radiofrequency signal that radio-frequency signal source produces antennas emission behind the filter and amplification through up-conversion.

Among Fig. 3, the chirp that naval target reflects amplifies after being received by receiving antenna, sends into low-converter and obtain the chirp baseband signal after filtering, send display unit to show image after sampling and imaging processing.

Fig. 4 looks around synthetic aperture imaging radar sea beam scanning synoptic diagram.Wherein upper figure has drawn two beam scanning situations around the receiving antenna of the axle center rotation of rotating shaft, in real work, can get final product with an antenna scanning, also can be with two, three even more antennas around the axle center rotation, as long as guarantee its rotation gravity balance.When adopting many antenna receptions, radar receiver can adopt multichannel form, also can adopt the mode that timesharing receives in turn between different antennae.Fig. 4 figure below has drawn under rotation status the synoptic diagram that concerns of target on the receiving antenna wave beam and sea.

Fig. 5 looks around the use view that synthetic aperture imaging radar is installed in the boats and ships upper brace, emitting antenna is launched chirp pulse signal while rotating, receive simultaneously the chirp pulse signal that is reflected by naval target, send into the back circuit and carry out imaging processing and demonstration.Wherein, dotted line is that signal entity antenna is in the rotation of relevant position.

Fig. 6 is the Doppler history synoptic diagram of static target in looking around synthetic aperture imaging radar on the sea.Because the rotation of receiving antenna, the sea static target can produce positive Doppler shift when entering radar beam, and when receiving antenna rotated to wave beam over against target, Doppler shift was zero, and when receiving antenna wave beam wide, Doppler shift is for negative.If itself has motion target, then Doppler history be the Doppler history that brings of above-mentioned course and target speed and.

Table 1 is a group system s main working parameters of looking around synthetic aperture imaging radar that is operated in X-band, and this group parameter only as an example.Need to specifically calculate the brakstaff parameter in the requirement of the aspects such as target detection, boats and ships space constraint according to the user during actual design.

Table 1

Two, the basic skills of signal processing of the present invention

The below introduces a kind of based on signal processing method of the present invention.

Because the picture that is polarized to of range Doppler algorithm Technologies Against Synthetic Aperture Radar is a kind of convenience and active data analysis mode, therefore, utilizing the range Doppler algorithm to process to look around the target position information under the endlessly polar coordinates that synthetic-aperture radar obtains is good selection approach.Process through Range compress, the signal of looking around the synthetic-aperture radar collection can be expressed as form:

$s\left(\mathrm{\&theta;}\right|R_c,{\mathrm{\&theta;}}_c)=e^{-\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">j</figure-callout>}4\mathrm{\&pi;}/\mathrm{\&lambda;R}\left(\mathrm{\&theta;}\right|R_c,{\mathrm{\&theta;}}_c)},|\mathrm{\&theta;}-{\mathrm{\&theta;}}_c|<{\mathrm{\&theta;}}_s/2=\mathrm{\&lambda;}/2L---\left(1\right)$

In the formula, θ is the radar scanning position angle, R _c, θ _cFor the target location shows under polar coordinates, and R (θ | R _c, θ _c) be the distance of radar antenna and target, λ is the radar electromagnetic wave wavelength, θ _sBe the coherent accumulation radian, L is receiving antenna size in the horizontal direction, and the coherent accumulation radian that radar is looked around is the restriction that is subjected to the receiving antenna beam angle.In like manner, the distance of radar antenna and target can be expressed as follows:

$R\left(\mathrm{\&theta;}\right|R_c,{\mathrm{\&theta;}}_c)=\sqrt{{{\mathrm{<figure-callout\; id="2"\; label="R\; c"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">R</figure-callout>}}_c}^2+r^2-{2R}_{c}r\cos (\mathrm{\&theta;}-{\mathrm{\&theta;}}_c)}---\left(2\right)$

In the formula, r is the length of rotating lever.To following formula at θ=θ _cThe place launches to obtain:

R(θ)＝R(θ _c)+R'(θ _c)θ+R''(θ _c)θ ²/2!+R'''(θ _c)θ ³/3!+... （3）

In the formula, R (θ _c)=R _c-r; R'(θ _c)=0; R''(θ _c)=R _cR/R (θ _c)=R _cR/ (R _c-r).Ignore the item formula that number of times in the formula is higher than secondary, utilize wave number Doppler parameter, can obtain:

R(θ)＝R(θ _c)-λu _Dc(θ-θ _c)/2-λu _R(θ-θ _c) ²/4+... （4）

And, doppler centroid u _Dc=0, Doppler shift

At this moment, the signal of reception can be expressed as:

$s\left(\mathrm{\&theta;}\right|R_c,{\mathrm{\&theta;}}_c){=e^{-\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">j</figure-callout>}4\mathrm{\&pi;}/\mathrm{\&lambda;R}\left(\mathrm{\&theta;}\right)}\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">e</figure-callout>}}^j---\left(5\right)$

Contain the noise linear with the position angle in this signal.

Here, the range Doppler matched filter is defined as follows:

$h^{-1}\left(\mathrm{\&theta;}\right)=e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}\&lsqb;u_{\mathrm{Dc}}\mathrm{\&theta;}+u_R{\mathrm{\&theta;}}^2/2\&rsqb;---\left(6\right)}$

To the data that receive according to following filtering mode carry out the orientation to compression process:

$\left(\mathrm{\&theta;}\right)={\&Integral;h}^{-1}({\mathrm{\&theta;}}^{\&prime;}-\mathrm{\&theta;})s\left({\mathrm{\&theta;}}^{\&prime;}\right){\mathrm{d\&theta;}}^{\&prime;}---\left(7\right)$

Wherein, the integrating range by θ ' is [θ _c-θ _s/ 2, θ _c+ θ _s/ 2] can further obtain:

$g\left(\mathrm{\&theta;}\right)=e^{-\mathrm{<figure-callout\; id="4"\; label="j"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">j</figure-callout>}4\mathrm{\&pi;}/\mathrm{\&lambda;}(R_c-r)}{\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">e</figure-callout>}}^j$

In the formula, sinc is sinc function Following formula g (θ) is at θ=θ _cThe place is for θ _sTo have maximal value.

Equally, the radar bearing angular resolution is defined as follows:

$\mathrm{\&delta;\&theta;}=\frac{\mathrm{\&lambda;}(R_c-r)}{{2R}_c{\mathrm{r\&theta;}}_s}---\left(9\right)$

Because the radar phase place is

Therefore, the image range of imaging is the target that always extends to detection from radar receiving antenna, rather than from the center of circular arc as starting point.Because the image that radar obtains under polar coordinates, shows that in order to use it for machine also need to be converted into the image under the rectangular coordinate, conversion formula is as follows:

x _c＝R _ccosθ _c,y _c＝R _csinθ _c （10）

x _c, y _cPositional information for target under the rectangular coordinate.Like this, Azimuth Resolution also can be exchanged into following formula:

${\mathrm{\&delta;\&theta;R}}_c=\frac{L}{2r}(R_c-r)---\left(11\right)$

Can be drawn by following formula, this also is one and R _cRelevant function, still, different from (9) formula is that it is irrelevant with wavelength X.In order to be applied to actual analysis, carried out simple calculating as an example of the X-band system example here.Work as r=4m, during L=0.15m, δ θ R _c=1.88 * 10 ^-2(R _c-r).Usually, than real aperture radar, looking around synthetic-aperture radar resolution will be its 11 times more than.

Three, the present invention's wave stream inverting rudimentary algorithm

Obtain the image on boats and ships periphery sea by looking around the SAR radar after, can be by the image sequence processing on continuous time being obtained wave and the Ocean current information in the boats and ships periphery number kilometer range.The below introduces a kind of disposal route, comprises two modules: pretreatment module and inverting module.

The function of pretreatment module is that the sea echo raw data of looking around the collection of synthetic aperture imaging thunder is carried out pre-service, mainly comprise seven steps such as Data Segmentation, distance are chosen, attenuation compensation, denoising, coordinate conversion, zone selection, pretreatment process figure such as Fig. 6.

The process flow diagram of inverting module such as Fig. 7.Utilization is looked around the synthetic aperture imaging thunder and is collected search coverage sea echo figure, and the echo sequence of collecting is saved as three-dimensional image sequence g (x, y, t), and x, y, t are the positional information of target under rectangular coordinate.The present invention is divided into each zonule for the processing of subsequent algorithm looking around synthetic aperture imaging thunder detecting area first, as: the area size of choosing of setting is L _x* L _yRice, the i.e. minimum N that is divided into of X-direction _xEqual portions, resolution are Δ x rice; The minimum division of Y direction N _yEqual portions are that resolution also is Δ y rice.Analysis of Radar image sequence quantity is chosen for the N width of cloth, considers the time (also being the time Δ t that radar antenna turns around) of every two field picture image, can draw the needed period of time T of this image sequence=N* Δ t.Wherein, Δ x, Δ y are radar resolution, and its value is relevant with the waveform bandwidth of radar system; L _x* L _yBe the size in inverting zone, be generally hundreds of rice;

After the sea echo raw data of collecting has been carried out pre-filtering processing as above, the sea echo gradation of image value g (x, y, t) that distributes with space-time that is converted to rectangular coordinate is made 3 dimension FFT, obtain the energy distribution in wave number space and frequency space

$\begin{array}{c}I(k_x,k_y,\mathrm{\&omega;})={\&Integral;}_0^{\mathrm{Lx}}{\&Integral;}_0^{\mathrm{Ly}}{\&Integral;}_0^{T}g(x,y,t)\exp \&lsqb;i(k_{x}x+k_{y}y-\mathrm{\&omega;t})\&rsqb;\mathrm{dxdydt}\\ =\underset{{\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">n</figure-callout>}}_1=1}{\overset{\mathrm{Nx}}{\mathrm{\&Sigma;}}}\underset{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">n</figure-callout>}}_2=1}{\overset{\mathrm{Ny}}{\mathrm{\&Sigma;}}}\underset{{\mathrm{<figure-callout\; id="3"\; label="n"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">n</figure-callout>}}_3=1}{\overset{N}{\mathrm{\&Sigma;}}}g(\mathrm{<figure-callout\; id="1"\; label="n"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">n</figure-callout>}1,\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">n</figure-callout>}2,n3)\exp \&lsqb;i({\mathrm{<figure-callout\; id="1"\; label="k\; x\; n"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">k</figure-callout>}}_x{n}_{}{}_1\mathrm{\&Delta;x}+{\mathrm{<figure-callout\; id="2"\; label="k\; y\; n"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">k</figure-callout>}}_y{n}_{}{}_2\mathrm{\&Delta;y}-{\mathrm{\&omega;<figure-callout\; id="3"\; label="n"\; filenames="HDA00003548453000011.png"\; state="\{\{state\}\}">n</figure-callout>}}_3\mathrm{\&Delta;t})\&rsqb;\end{array}---\left(12\right)$

Wherein, L _x, L _y, T is respectively length and width and the seasonal effect in time series total length of rectangular area.

L _x＝N _xΔx

L _y＝N _yΔy

T＝NΔt

Spectral resolution after the conversion is ${\mathrm{\&Delta;k}}_x=\frac{2\mathrm{\&pi;}}{L_x},{\mathrm{\&Delta;k}}_y=\frac{2\mathrm{\&pi;}}{L_y},\mathrm{\&Delta;\&omega;}=\frac{2\mathrm{\&pi;}}{T}.$

Namely can obtain the sea echo power spectrum to the three-dimensional spectrum after the conversion is squared.By the sea echo power spectrum, can be by obtaining the size and Orientation of ocean surface ocean current and Water Depth Information with the linear wave theory dispersion equation of flow velocity in conjunction with least square method.

$\mathrm{\&omega;}=\sqrt{\mathrm{gk}\tanh \left(\mathrm{kd}\right)}+k_x{u}_x+k_y{u}_y---\left(13\right)$

In the formula, ω is theoretical wave frequency, and k is the wave number amplitude, k _x, k _yRepresenting respectively the x coordinate axis of regulation and the wave number of y coordinate axis.This linear wave theory dispersion equation is subject to u _x, u _yLinear effect, but with depth of water d be nonlinear relation.After drawing Ocean current information, can on the basis of ocean current, carry out filtering to data, then filtered data be carried out the extraction of Wave Information, can obtain namely that wave is high, wave is to information such as, wave cycle, wavelength.

Claims (5)

1. look around synthetic aperture imaging radar for one kind, it is characterized in that: comprise transmitter unit (1), reception, amplification, down coversion and filter unit (2), signal is processed and image-generating unit (3), display unit (4), radio frequency signal generation unit (5), control module (6), the propulsion system (7) that the control dual-mode antenna rotates;

Control module (6) respectively with transmitter unit (1), reception, amplification, down coversion and filter unit (2), display unit (4), radio frequency signal generation unit (5), the propulsion system (7) that the control dual-mode antenna rotates connect;

Transmitter unit (1) respectively with radio frequency signal generation unit (5), the propulsion system (7) that the control dual-mode antenna rotates connect; Reception, amplification, down coversion and filter unit (2) respectively with radio frequency signal generation unit (5), signal is processed and image-generating unit (3), propulsion system (7) connection that the control dual-mode antenna rotates; Signal is processed and is connected 3 with image-generating unit) be connected with display unit (4).

2. a kind of synthetic aperture imaging radar of looking around according to claim 1 is characterized in that: described transmitter unit (1) comprises frequency-modulated wave generator, up-converter circuit, power amplification circuit and the emitting antenna that connects successively; The output terminal of radio frequency signal generation unit (5) is connected with the input end of up-converter circuit.

3. a kind of synthetic aperture imaging radar of looking around according to claim 1 and 2 is characterized in that: described reception, amplification, down coversion and filter unit (2) comprise receiving antenna, amplifying circuit, down coversion and the filtering circuit that connects successively; The output terminal of radio frequency signal generation unit (5) is connected with the input end of down coversion and filtering circuit.

4. a kind of synthetic aperture imaging radar of looking around according to claim 3 is characterized in that: described signal is processed and is connected 3 with image-generating unit) comprise the digital sample circuit, imaging signal processing and the imaging circuit that connect successively.

5. a kind of synthetic aperture imaging radar of looking around according to claim 4 is characterized in that: the propulsion system (7) that described control dual-mode antenna rotates comprise antenna rotating platform and control circuit thereof; Be fixed with rotating shaft on the antenna rotating platform, control circuit control emitting antenna and receiving antenna rotate around the axle center of rotating shaft.

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